Numerous steps are involved in the fabrication of microelectronic structures. Within the manufacturing scheme of fabricating integrated circuits selective etching of semiconductor surfaces is sometimes required. Historically, a number of vastly different types of etching processes, to selectively remove material, have been successfully utilized to varying degrees. Moreover, the selective etching of different layers, within the microelectronic structure, is considered a critical and crucial step in the integrated circuit fabrication process.
Increasingly, reactive ion etching (RIE), is the process of choice for pattern transfer during via, metal line and trench formation. For instance, complex semi-conductor devices such as advanced DRAMS and microprocessors, which require multiple layers of back end of line interconnect wiring, utilize RIE to produce vias, metal lines and trench structures. Vias are used, through the interlayer dielectric, to provide contact between one level of silicon, suicide or metal wiring and the next level of wiring. Metal lines are conductive structures used as device interconnects. Trench structures are used in the formation of metal line structures. Vias, metal lines and trench structures typically expose metals and alloys such as Al, AlCu, Cu, Ti, TiN, Ta, TaN, W, TiW, silicon or a suicide such as a suicide of tungsten, titanium or cobalt. The RIE process typically leaves a residue (of a complex mixture) that may include re-sputtered oxide material as well as possibly organic materials from photoresist and antireflective coating materials used to lithographically define the vias, metal lines and or trench structures.
It would therefore be desirable to provide a selective cleaning material and process capable of removing remaining photoresist as well as the residues caused by selective etching using plasmas in general and RIE specifically. Moreover, it would be desirable to provide a selective cleaning material and process, capable of removing the photoresist and etching residue, that exhibits high selectivity for the residue as compared to metal, silicon, silicide and/or interlevel dielectric materials such as deposited oxides that might also be exposed to the cleaning composition. It would be especially desirable to provide a composition that is compatible with and can be used with such sensitive low-k films as HSQ, MSQ, FOx, black diamond (can you identify these chemically) and TEOS (tetraethylsilicate).
Along these lines, fluoride-containing stripers are usually too aggressive toward sensitive films with low dielectric constant such as HSQ and porous MSQ films.
For example, eventhough formamide is a good protic solvent, it was found that formulations with formamide had decreased compatibility with FOx® films. See Parker, Advances in Organic Chemistry, 5, 1 (1965)